Recently, in the field of production of circuit formed materials, such as electronic circuit substrates, there has been a demand to reduce production cycle time and to improve operating efficiency of manufacturing facilities by reducing setup time when changing production models. In such setup time for a component mounting apparatus, it is important to fix a component supply unit so as to accurately position components at predetermined pick up locations of the component mounting apparatus. Especially, in order to respond to recent trends of miniaturization and weight reduction of electronic equipment, density of mounted components on a circuit formed material has increased. As a result, a component itself tends to be smaller, and hence even further accurate positioning of components at a setup time is required.
One known way to reduce setup time is simultaneous changing of supplying devices. When production of one specific model is completed, and a new model production is to be started, it is necessary to change a plurality of supplying devices, such as cassettes, for supplying a variety of components needed for production of the new model. Since numbers of different components are normally mounted on a single circuit formed material, it takes a considerably long time to change all of cassettes carrying these components. Simultaneous changing of a plurality of supplying devices, which may be conducted outside of the component mounting apparatus, has made it possible to complete these time consuming changes prior to a next setup timing. Consequently, setup may be performed in an efficient manner. In order to perform this simultaneous changing smoothly, a cart for changing component supply units (hereinafter, referred to as a “cart”) is used.
A component supply unit for holding a plurality of supplying devices as well as the cart for mounting and transporting the component supply unit are required to satisfy conditions such as accurate positioning capability, low cost, stability and easy handling. In the course of aforementioned trends of miniaturization of components and increasing of component mounting density, further improvement of accurate positioning for a purpose of repeated setup is required.
Now, a component mounting apparatus and a cart of prior art is described by referring to the appended drawings. In the following explanation, a substrate is used as a representative of circuit formed materials. In recent years, however, components may be mounted even on a casing of electronic equipment. Therefore, a term “substrate” used hereinafter includes all these kinds of materials in addition to an electronic circuit substrate. FIG. 17 schematically illustrates an overall view of a conventional component mounting apparatus. Referring to FIG. 17, a transferring device 101 transfers a substrate 102 into and out of the component mounting apparatus, and holds the substrate at a predetermined position while a component 103 is being mounted on it. In order for a mounting head 108 to perform a series of operations, such as sucking a component 103 from a component supply unit 106 (tray type) or 107 (cassette type), and mounting the component 103 onto the substrate 102, XY robot 104 transports the mounting head 108 toward these predetermined positions and holds it at the positions. Recognizing camera 109 images and recognizes a condition of sucked component 103 while the component 103 is being held by the mounting head 108.
Next, an operation of the component mounting apparatus structured as above is described. The substrate 102 is transferred to a mounting position and firmly held by the transferring device 101. The XY robot 104 transports the mounting head 108 to a position just above the component supply unit 107, and each nozzle attached to the head 108 sucks a component 103 for picking up these components. A condition of the component 103 sucked by each nozzle is imaged by the recognizing camera 109. Based on information recognized and obtained by the camera 109, necessary adjustment of a position of the mounting head 108 and an angle of the components 103 is made, and then the mounting head 108 mounts the component 103 on a predetermined mounting position of the substrate 102.
Next, the component supply unit 107 for holding a plurality of cassettes 112, and a cart 120 used for simultaneous changing of a plurality of cassettes 112 are described. After a plurality of cassettes 112 are attached to the component supply unit 107, the component supply unit 107 is installed on the component mounting apparatus and positioned by engaging with two positioning pins 114 provided at a fixing device 113 of the component mounting apparatus. FIG. 18 shows a schematic perspective view of the cart 120 used for installing the component supply unit 107 onto the component mounting apparatus. Referring to FIG. 18, the cart 120 mainly comprises a base frame 121, lifter 122, holder 123, and a handle 124. The base frame 121 includes a movable and maneuverable trolley having four total wheels including two caster wheels. A lift pedal 126 is provided on the base frame 121 for operating a hydraulic jack to lift or lower the holder 123.
The component supply unit 107 is mounted on a central portion of U-shaped holder 123, which is supported by the lifter 122. At both ends of the holder 123 in an X direction of FIG. 18, positioning bars 127 having a pair of protrusions for each are provided for positioning the cart 120 in a Z direction of this figure. When the cart 120 is moved toward the component mounting apparatus in a Y direction for installing the component supply unit 107 onto the component mounting apparatus, the positioning bars 127 engage with corresponding guides provided on the component mounting apparatus. Each protruded end of the bar 127 has a tapered portion which makes engagement with the guide easier. The handle 124, structured by a pair of bars, is used by an operator for maneuvering the cart 120 structured as above.
Now, a setup operation of the component supply unit 107 after completion of a production of one model and before starting production of another model is described. Referring back to FIG. 17, a cassette 112 carrying components needed for a model of completed production is still fixed to the component mounting apparatus at one of the fixing devices 113. A vacant cart 120 is moved forward to the fixing device 113. The component supply unit 107 is pulled back onto the holder 123 of that cart 120, and then lift pedal 126 is operated for lifting holder 123. By this operation, the component supply unit 107 installed on the component mounting apparatus is lifted from the component mounting apparatus and held by the holder 123. When the cart 120 is moved backward together with the component supply unit 107, all the cassettes 112 installed on the component supply unit 107 are removed from the component mounting apparatus at once by performing a single operation.
Next, a different component supply unit 107 holding a plurality of cassettes 112 for a next production model is mounted on the holder 123 of the cart 120. The operator moves this cart 120 forward to the fixing device 113 of the component mounting apparatus. Then, the operator operates lift pedal 126 for lifting up holder 123 together with the component supply unit 107. The cart 120 is then further moved forward, and after the operator confirms that U-shaped slots provided in the component supply unit 107, which will be described in detail later, engage with locating pins 114 provided on the fixing device 113, the operator again operates the lift pedal 126 for lowering the component supply unit 107. The component supply unit 107 is now positioned firmly on the fixing device 113 of the component mounting apparatus. After the component supply unit 107 is installed, vacant cart 120 is pulled backward, and production resumes.
FIG. 19 shows the component supply unit 107 viewed from its bottom, illustrating a positioning mechanism for fixing the unit 107 to the component mounting apparatus. When the component supply unit 107 is mounted on the component mounting apparatus, the component supply unit 107 is pushed forward to a base line of the component mounting apparatus shown by a double-dashed line A—A. In this figure, a bottom surface of the component supply unit 107 comprises base plate 116. This base plate 116 functions as a reference plane for positioning the component supply unit onto the component mounting apparatus in a horizontal direction.
Extended portions 117 and 118, are formed in the vicinity of both ends of the base plate 116 in an X direction, each of which has a U-shaped slot 119 facing the component mounting apparatus. By pushing both of the extended portions 117 and 118 firmly against the double-dashed line A—A, the component supply unit is positioned relative to the component mounting apparatus in a Y direction shown in FIG. 19. And when the positioning pins 114 located on the fixing device 113 of the component mounting apparatus fit into the U-shaped slots 119 formed at both extended portions 117 and 118, the component supply unit is positioned firmly on the component mounting apparatus in the X direction. After the component supply unit is fixed in position, a clamp, not shown in this figure, is operated for fixing the component supply unit 107 to the component mounting apparatus, thereby readying the component mounting apparatus for resuming a component mounting operation.
In FIG. 19, the U-shaped slots 119 are formed at both extended portions 117 and 118. It is known, however, that U-shaped slot 119 may be formed at only one of the extended portions 117 or 118, and the other portion 117 or 118 may have a flat surface which contacts with the reference plane formed at a component mounting apparatus side. In either case, the positioning pins 114 and the U-shaped slot(s) 119 are to be tightly engaged with each other in order to position the component supply unit 107 on the component mounting apparatus. Therefore, the operator is required to perform a technique to properly move the cart 120 for achieving this tight engagement between the positioning pins 114 and the U-shaped slot(s).